Observations of tides and waves in the middle atmosphere using Indian MST radar

Abstract

Attempt has been made to detect and study the tidal oscillations and waves in the tropical middle atmosphere using Indian MST radar. The tidal oscillations above 8 km with amplitude as large as ~5.8 ms^-1 are observed both in diurnal and semi-diurnal zonal wind. A clear downward phase progression is seen from an altitude 16 km to 10 km in the diurnal component. The observed amplitudes are much larger than that predicted by classical tidal theory. The episodic type of oscillations above 12 km both in zonal and meridonial winds indicate the presence of waves with a vertical wavelength of about 3 km and with a periodicity of ~4 days. These characteristics of the waves lead to their identification as Mixed Rossby Gravity (MRG) waves.